This invention relates generally to abrasive wear components and, more particularly, to high energy treated polycrystalline diamond compact (“PDC”), cubic boron nitride (“CBN”) cutter, and other similar type cutter substrates and the methods of manufacturing such items.
Typically, down hole tools including, but not limited to drill bits and reamers, have a plurality of blades that have a plurality of cutters or inserts coupled to each of the blades. These plurality of cutters may include, but is not limited to, tungsten carbide inserts, PDC cutters, CBN cutters, and thermally stable polycrystalline diamond cutters. PDC cutters are fabricated by pressing a diamond layer onto a tungsten carbide substrate, or similar substrate, to create a highly wear resistant layer or cutter face. Similarly, CBN cutters are fabricated in the same manner except that a CBN layer is pressed in lieu of a diamond layer.
The substrate is typically formed by combining grains of a metallic material, such as tungsten carbide, with a binder material, such as cobalt, to form a composite material. This composite material is pressed into a desired shape and heated, sometimes under pressure, such that the binder material liquefies and cements the grains of abrasive material together. The cemented abrasive component is then allowed to cool and ground into shape to form the substrate. Higher concentrations of cobalt increases the toughness, but decreases the hardness or abrasion resistance.
As the down hole tool is rotated, the cutters scrape against the bottom and sides of the borehole to cut away rock. As the rate of penetration of the down hole tool increases, the effective life of these cutters is substantially decreased because the cutters become cracked and occasionally are violently torn from the blade. Thus, there is a need for fabricating cutters with greater hardness and toughness traits so that their effective life may increase.
With respect to tungsten carbide inserts, High Energy Tumbling, as disclosed in U.S. Pat. No. 7,258,833 (the “'833 Patent”) issued to Rainey et al. on Aug. 21, 2007, has been used successfully to treat the tungsten carbide inserts in a way that work hardens the outer surface of the inserts while maintaining the core toughness of the inserts. This treatment creates inserts that are more resistant to both fracture breakage and to abrasive wear than untreated inserts. This process also acts to screen out inserts with significant but indiscernible flaws that would otherwise be used and fail prematurely.
With respect to PDC cutters, CBN cutters, and other similar type cutters, these cutters fail through breakage of the substrate at a rate estimated to be about 4% to about 8% of the time. Thus, PDC cutters, CBN cutters, and other similar type cutters having a highly wear resistant cutter face also may benefit from a surface treatment of the substrate equivalent to the High Energy Tumbling process to reduce the failure rate from substrate breakage suffered when in use. However, since the diamond layer of PDC cutters and the CBN layer of CBN cutters are extremely brittle, the High Energy Tumbling process would damage the layer thereby destroying the usefulness of the cutters, especially in drilling applications. Thus, the High Energy Tumbling process does not provide an effective method for treating PDC cutters, CBN cutters, and other similar type cutters when the entire fabricated cutter with the wear resistant layer is subjected to the process.
Additionally, treating the substrates in the High Energy Tumbling process prior to pressing the diamond layer or CBN layer is not a viable option because the benefits of the treatment would be substantially reversed during the High Pressure High Temperature press that is typically used to press the wear resistant layer to the substrate. Thus, the High Energy Tumbling process does not provide an effective method for treating the substrates of PDC cutters, CBN cutters, and other similar type cutters prior to pressing the diamond layer or CBN layer.
In view of the foregoing discussion, need is apparent in the art for improving the PDC cutters and the CBN cutters so that the life of the cutters are increased. Additionally, a need is apparent for providing effective surface treatment of the substrates for PDC cutters, CBN cutters, and other similar type cutters similar to that accomplished by the High Energy Tumbling process for tungsten carbide inserts, but accomplished in such a manner that the brittle diamond layer of the PDC cutter and the CBN layer of the CBN cutter are not damaged by the process. A technology addressing one or more such needs, or some other related shortcoming in the field, would benefit down hole drilling, for example creating boreholes more effectively and more profitably. This technology is included within the current invention.